Since an inmold decoration product including a silver-plating layer on a plastic material exhibits an appearance like a metal, it can be used in automobile interior parts such as a meter cluster, a center cluster, a center console, etc.; automobile exterior parts such as wheel caps, a bumper braid, wheel garnishes, a grille radiator, a back panel, door mirror covers, door handles, etc.; and applications other than automobile's parts such as an air conditioner's housing, a cellular phone, a notebook computer, a cosmetic case, etc.
However, a decorative multilayer coating film, which contains a silver-plating layer, has a problem that the silver-plating layer is discolored or exhibits whitish haze in testing the coat performance according to a salt spray test or after a lapse of a long time and therefore it loses design value.
As a method of improving such a problem, there is described a method of producing plated products comprising the step of removing a trace of impurities existing on the metal surface artificially in Japanese Kokai Publication 2002-256454. But, in such an approach, since number of steps increases, it was not efficient and its effect was not adequate.
In Japanese Kokai Publication 2002-256455, there is described a plated product which protects corrosion from extending throughout a metal-plating layer when the corrosion is generated by purposefully forming microcracks in the metal-plating layer to prevent the degradation of design. However, since such an approach does not essentially prevent the corrosion of metal itself, its effect is limited and a beautiful appearance cannot be maintained for a sufficiently long time.
In Japanese Kokai Publication 2003-155580, there is described a method of retarding the corrosion of metal by including a coating layer comprising a specific silicon acrylic resin to inhibit the permeation of water into a metal-plating layer. But, it is desired to enhance its effect more and to realize a higher level of protection of corrosion.